Various types of lamps lit for safe driving are installed in a vehicle, and there are turn signal lamps, brake lamps, backup lamps, tail lights, emergency lights and the like on the rear side of the vehicle. The turn signal lamps perform a function of informing other vehicles or pedestrians of left and right traveling directions of the vehicle, which are mainly yellow color and flicker at regular intervals of one or two times a second. The brake lamps are red color and inform following vehicles that the vehicle is stopping when the driver stops the vehicle by stepping on the brake pedal. The backup lamps give a caution to following vehicles or pedestrians when the vehicle moves backwards, and the tail lights inform following vehicles of the presence of the vehicle at night. The emergency lights are lamps for indicating an emergency situation or a warning, which flash in orange color. In addition, a design which integrates these lamps in one piece is referred as a rear combination lamp. Other than these, there are side lights independently installed in the bumper to inform the width of the vehicle, a license plate light for illuminating the license plate, and the like.
The rear combination lamp informs following vehicles of the presence of the vehicle as the tail light is lit at night and performs an important function for maintaining a distance between the vehicle and the following vehicle while the vehicle runs.
However, the rear combination lamp is disadvantage in that it does not have a function of giving a special caution or warning when the driver of the following vehicle approaches the vehicle within a safe distance at a speed higher than that of the vehicle without reducing the speed in response to braking of the vehicle, abrupt natural reduction in speed, stopping of the vehicle in an emergency case, or the like, and when the following vehicle approaches too close, it may cause a rear-end collision as the late braking of the following vehicle cannot prepare for an unexpected situation or the like.